Aircraft Cabin Door Pressure Vent System

ABSTRACT

Disclosed is an aircraft door including a handle-activated pressure relief system that avoids potentially dangerous pressure differences between the cabin and the atmosphere outside the aircraft. A flow path is created between the inboard and outboard handles on the door. A pressure vent door is located in the flow path. The vent door being is opened when either of the inboard and outboard handle assemblies are activated. Once either handle is rotated beyond a particular point, a spring in the supporting mechanics becomes over-center. At the same time, the vent door comes under the influence of a magnet, snapping the vent open. After the door has been opened, it can be relatched by operating the handles in the reverse direction. The magnet and spring hold the vent door open until the aircraft door is fully latched, sealed, and secured. Only then does the vent door sealingly close.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/238,785 filed Sep. 1, 2009, the entire contents of which are hereinincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to methods of aircraft door design andsafety. More specifically, the invention relates to the field ofreleasing air to drop cabin pressure prior to or instantaneously uponthe opening of a door.

2. Description of the Related Art

It is known in the art to include a door vent in an aircraft door.Normally this type of arrangement includes a vent door that is locatedremotely from the door handle. In many cases the handle is mechanicallyconnected to the vent door to cause it to open when the door is opened.See e.g., U.S. Pat. Nos. 6,457,675 issued to Plude et al.; 5,931,415issued to Lingard et al.; 6,454,210 issued to Plattner; 5,823,473 issuedto Odell et al.; 5,305,969 issued to Odell et al.; 4,473,201 issued toBarnes et al.; 5,337,977 issued to Fleming et al.; 7,207,524 issued toPuschman et al.; 4,720,065 issued to Hamatani; and 2,748,855 issued toSiems et al.

SUMMARY

The present invention is defined by the claims below. Embodiments of thedisclosed systems and methods include arrangements used to relieve cabinpressure before or instantaneously upon opening an aircraft door.

In one embodiment, an aircraft door includes an inboard handle assemblyand an outboard handle assembly. A flow path is created for allowing airto pass into the inboard handle assembly and then out of the outboardhandle assembly. In another embodiment a pressure vent door is locatedin the flow path. The vent door being is opened when either of theinboard and outboard handle assemblies are operated. When the vent dooris opened, pressure is released from the cabin.

In some embodiments the inboard handle assembly includes a plurality ofslots created by standoffs included between an interior surface of theaircraft and the handle assembly. The slots are a part of the flow pathcreated. In embodiments the outboard handle assembly includes anair-exhausting aperture, and a plurality of smaller apertures locatedunderneath a release pawl to allow air to be directed outward from thehandle assembly.

Another embodiment is a pressure relief system for an aircraft door thathas a door handle mechanically connected to cause rotation of a firstshaft when activated. The rotation of the first shaft adapted to open apressure vent. A spring closes the pressure vent when eitherunder-center or over-center, and opens the pressure vent when returnedto either under-center or over-center position. In embodiments thepressure vent is on a pivot, a magnet holds the pressure vent in openposition after the handle is pulled, and the magnet releases thepressure vent only when the handle is returned and the door is closed.

In some embodiments a backbone, or spine member is translated uponrotation of the first shaft. The backbone member then causes rotation ina second shaft. A lever is provided on the second shaft. In thisembodiment, the lever determines whether the spring is in an over-centeror under-center position depending on an angular position of the lever.

Another embodiment is a method. More specifically, a process foravoiding an unsafe pressure differential between the outside and insideof an aircraft door. This method includes the steps of: (i) locating aninboard handle in an inboard handle housing on the inboard of theaircraft door; (ii) locating an outboard handle in an outboard handlehousing on the outboard side of the aircraft door; (iii) creating aventable airpath through both the inboaurd and outboard handle housings;and (iv) causing the airpath to open upon activation of either of theinboard or outboard handles. In one version the airpath remains openunless the door is secured as a safety feature. In another possiblevariation of the vent door, the handle, when released, opens up abruptlyto release. The release can be triggered using the angular position of aspring to cause it to become over-center and create a reverse inleverage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Illustrative embodiments of the present invention are described indetail below with reference to the attached drawing figures, which areincorporated by reference herein and wherein:

FIG. 1 is side view of an aircraft in which embodiments of the disclosedsystems could be used;

FIG. 2 is an inboard view of a full aircraft door in which embodimentsof the disclosed systems could be used taken from a perspective that isoutside the aircraft;

FIG. 3 is an outboard view of the aircraft door from inside theaircraft;

FIG. 4 is an outboard view of the aircraft door from inside the aircraftwith the door cover panel removed to reveal the internals;

FIG. 5 is a perspective view of one embodiment for the inside doorhandle assembly of the present invention from inside where the vent dooris in a closed position;

FIG. 6 is a perspective view of the FIG. 5 embodiment for the inboarddoor handle assembly of the present invention, taken from a differentangle than that shown in FIG. 5 where the vent door is in an openposition;

FIG. 7A shows a front view of the internals of the disclosed embodimentof the cabin door vent system;

FIG. 7B shows a perspective view from below highlighting ahandle-to-handle mechanical linking system of disclosed embodiment forthe cabin door vent system;

FIG. 7C shows a perspective view from slightly below and lefthighlighting the mechanical over-center vent control system of thedisclosed embodiment;

FIG. 7D shows a perspective view from above left which reveals themechanical systems which use the translation of the door backbone tocause the opening and closing of the disclosed embodiment;

FIG. 8 is a side view of the door vent systems from inside showing theover-center relationship used to open and shut the pressure vent door;

FIG. 9 is a perspective view of the outboard door handle assembly of thepresent invention where the outboard handle is in an open position;

FIG. 10 is a broken out view of the vent system internals showing airflow paths created through the handle assemblies;

FIG. 11 shows a view of a vented interior handle frame, and morespecifically, how handle surrounding air passageways are created to aidin venting; and

FIG. 12 shows the interior handle frame from an angle in which the airpassageways are visible.

DETAILED DESCRIPTION

Embodiments of the present invention provide systems and a method forrelieving cabin pressure in an aircraft prior to or instantaneously uponthe door being opened, but before the door becomes unlatched.Additionally, vent door system disclosed keeps cabin pressure below acertain acceptable level (e.g., 0.5 psig cabin pressure differential) ifthe door is not fully closed, latched, and locked. The vent doorassembly was designed to meet this maximum cabin differential pressurecriterion (e.g., 0.5 psig) up to an aircraft altitude of 15,000 feet,which is the most critical altitude. This is accomplished bymechanically driving the pressure-vent door to open and close inresponse to upward and downward translations of a backbone which is usedto trigger the door latches of the aircraft.

The vent door is sequenced to be the last element to move into positionwhen the system moves into the latched and locked state, and the firstcomponent to move in the open direction as the system moves into theunlatched and unlocked position. Thus, upon opening, the pressure isrelieved prior to or instantaneously upon unlatching of door. Also,because the vent door is the last element to be moved into position whenthe door is latched, any failures to completely close the door will bedetected by the pilot as a lack of cabin pressure since the vent willremain open unless there is proper closure.

Another feature of the disclosed system causes the vent door to remainopen if there is a mechanical failure in the door opener system. In oneembodiment, this subsystem incorporates a magnet which retains the doorin open position until acted on by a return force.

Another desirable result of venting through the existing door handles isthat there is no need for an additional pressure vent arrangement.Conventional arrangements, in some cases, include vent doors which arehandle activated. These arrangements, however, typically necessitate avent door which is located in some other place on the outside of theaircraft. This type of exterior door creates unnecessary drag. In someinstances, the aircraft exterior is modified to minimize theseaerodynamic effects, but this type of fix (e.g., extending fairings)normally results in undesirable weight increases. Thus, creating ahandle-to-handle air vent enables the outside of the aircraft to bestreamlined to a greater extent, and results in overall weightreduction.

System Environment

FIG. 1 shows an aircraft 100 having a door 102 with a handle 106 inwhich the disclosed venting systems can be utilized. Referring to thefigure, the particular door 102 is a fuselage door. Immediately behindand below door 102 is a fairing 104. Fairing 104 is a protective shellformed over rough equipment in order to maintain a smooth aerodynamicexterior.

Referring now to FIG. 2, it can be seen that the outside of door 102includes a concealed hinge support 204 which not only secures door 102within a doorway defined in the walls of aircraft 100 (doorway notshown), but enables the door to open outwards. Defined into an outersurface 206 on the outside of door 102 is an outboard handle assembly106 having a key operated lock 210. A sight glass 212 enables the viewerto see an internal warning flag that, if missing, indicates possiblefailures in operation. Handle assembly 106 is included in a housing 213.

Those skilled in the art will recognize that handle assembly 106 is thesort that has an upper release pawl 209 which, when depressed, releasesa lower lever portion 211 of the handle 106. Once lever 211 has beenunlatched, it can be rotated out and down towards the position shown inFIG. 9. This rotation causes a plurality of securing latching members214 on the outside of the door to retract laterally inward, and thus, bedrawn out of reciprocating receptacles (not shown) in the surroundingframe structures which define the door opening. The retraction ofmembers 214 out of the door frame enables the door to be opened.

FIG. 3 shows the door as viewed from the inside of the aircraft. Hingedsupport 204 and securing latch members 214 can also be seen in thisview. Also shown is an inside cover 302. The upper and lower portions ofcover 302 follow the contour of the aircraft, but towards the middle ofthe door, an outcropped portion 304 of the cover 302 extends up and downin a substantially vertical plane and includes an inboard door handleassembly 308. Like with the outboard handle, inboard handle assembly 308is included in a housing and has an upper portion that is an upperrelease pawl 309 which when depressed releases a lower lever portion 311of the handle assembly 308. Once inboard lever 311 has been unlatched,it can be rotated out and down. Like with the outboard lever 211,pulling inboard lever 311 causes the securing latch members 214 toretract out of reciprocating receptacles (not shown) in the surroundingdoor structures (not shown). This enables the door to be opened from theinside. The inside door has many more sight glasses 312 than does thedoor on the outside. Again, these enable the user to see flags, theabsence of which are an indication of malfunction.

FIG. 4 shows the inside of the door 102 from the same perspective asshown in FIG. 3, but with the cover portion 202 removed to reveal themechanical arrangement hidden behind it. Referring to FIG. 3, lever 311when rotated out and down causes a drive shaft 402 to rotate. When thisoccurs, linkage 403 rotates inward (see also FIG. 7) putting component405 in tension thus causing a vertical member/backbone 404 to be drivenupward causing a plurality of hinged lateral tension members 406 (seeFIG. 4) to mechanically pull the securing latches 214 inward from thereceptacles in the surrounding door structures, and the door may thus,be opened.

The Pressure Vent System

The ventilation arrangement is shown in detail in FIGS. 5-10. Referringfirst to FIGS. 5-8, an internal mechanical arrangement is shown whichcauses the opening of a pressure vent door 522 upon the unlatching andpulling either of outboard lever 211 or inboard lever 311. Morespecifically, when either of levers 211 or 311 is rotated out and down,the door is unlatched and also vented. When the door is then closed andrelatched, pressure vent door remains open until the securing latches214 are fully secured into receiving areas created in surrounding doorstructures (not shown). Once the latches 214 are completely secured intothe surrounding door housing, then the vent door 522 shuts and sealscompletely enabling pressurization of the cabin.

Handle-to-Handle Mechanical Link

Referring to FIG. 7B, it can be seen that outboard lever 211 is linkedto inboard lever 311 as follows. The lower portion of lever 311 isconnected to shaft 402. When a user pulls inboard lever 311, shaft 402rotates outward and down. Collar 502, which is mounted onto and rotateswith shaft 402. A fork 801 on collar 502 rotates into the page and up(as seen in FIG. 7B). The top of a push rod 802, which is pin linked to,and depends down from fork 801, will move upward and into the page (seeFIG. 7B) when handle 311 is thrown. The bottom of push rod 802 is pinlinked (via pivot link 804) to a receiving fork 805. Thus, the upwardmovement of rod 802 results in the rotation of receiving fork 805 abouta shaft (not shown, but is inside of the lower portion 808 of theoutboard handle housing as shown in FIG. 7B) which is linked at thebottom of outboard handle 211.

When a user pulls outboard handle 211, the opposite actions occur inthat receiving fork 805 rotates upward pushing rod 802 upward againstthe pin connection on forked extension 801 on collar 502. This causesshaft 402 to rotate such that handle 311 is rotated outward. Thus, thetwo handles are coupled to, and can both be activated to rotate commonshaft 402. Also, they are live handles in that they rotationally openand close together.

Pressure-Vent-Operating System

The pulling of either the inboard or outboard handles will also resultin the opening of pressure relief door vent 522. As discussed already,the two levers 211 and 311 move together, and when either is thrown,shaft 402 and collar 502 are driven in a counter clockwise direction(when looking outward from an inboard position as shown in FIG. 7B).Collar 502 also has a second fork 403 which depends downward and makes apin connection 812 with a tension link 405. Thus, upon thecounter-clockwise rotation of collar 502 upon throwing of either lever(211 or 311), tension link 405 will be pulled upward. Link 405, at thebottom has a pin connection 807 to a flange 809 on a bracket 811 (seeFIG. 7B) which is part of a backbone 404. Backbone 404, therefore, movesupward when either of levers 211 or 311 are pulled.

As explained already, when backbone 404 is translated upward upon leveractivation, it causes the retraction of latches 214 (see FIGS. 2 and 3)which allows the door to be opened when the latches are fully retracted.This backbone translation is also utilized to open the pressure ventdoor 522 to safely release cabin pressure before the aircraft cabin door102 is opened at all.

As can be seen in FIGS. 7C and 7D, the upward translation of backbone404 upon the activation of either handle 211 or 311 opens the pressurevent door 522 using an additional mechanical system. A laterallyextended pin 816 (See FIG. 7D) on the backbone 404 on engages integratedcatch portions 820 and 821 associated with collars 822 and 823,respectively. Collars 822 and 823 are bolted to vent drive shaft 519.The pin is fixed atop bifurcated mounts 818 on a bracket 819 that islocated on the backbone 404. The pin 816 is position along backbone 404in a position such that it engages the catches after the backbone hasalready been displaced upward a slight distance. Thus, the engagement ofthe catch portions 820 and 821 is not immediate, but delayed slightly.Upon engagement of the catches 820 and 821 (after backbone 404 hastranslated upward the slight distance), the resulting rotation of shaft519 causes a pair of upwardly (and inwardly) extending integrated levers824 (See now FIG. 7C) on collars 826 to rotate out. This puts member520, which pivotally connected between an upper portion of the door 522using a pin 833/fork 831 arrangement and the integrated lever 824 usinga similar pin 823/fork 829 arrangement, in tension.

This tension created enables pressure vent door 522 to pivot open.Conversely, the door 522 will shut if and when the backbone translatesdownward. Thus, the door can be moved between open and shut positionsdepending on backbone 404 translation, since the pressure vent door 522is hinged. The specifics regarding the hinge mount for the door 522 canbest be seen in FIG. 7C. The door is hinged using a short pivot axle 536mounted between two flanges 531 that extend out of the frame.

Thus, these features enable the pressure vent system to operate in openand closed modes. The closed mode exists when the handles are in theupright positions shown in FIGS. 2-5. Conventionally, this type ofhandle includes a latching mechanism, e.g., release pawls 209 and 309,which must be pushed in to release the levers, e.g., levers 211 and 311respectively. These latches also enable the levers to be secured backinto a secured position. When either of levers 211 or 311 is unlatchedand then rotated down, the system will be placed into the open modeshown in FIG. 6. In terms of semantics, this second “open” mode shouldbe construed as meaning any mode in which the pressure vent is opened atall—even minimally. By “closed mode,” it is meant that the pressure ventsystem is substantially sealed in a manner that enables cabin pressureto be maintained to an acceptable extent. Any specific degree ofopenness or closure is not intended in these meanings.

The Over-Center System

It is an advantage that pressure vent door 522 be dramatically snappedopen from the closed position shown in FIGS. 7A-D into the second“opened position” shown in FIG. 6. More specifically, the systemscontrolling the pivoting of pressure vent door 522 are adapted such thatthe door opens before the disengagement of the door latches 214 uponopening, and also so that the vent door 522 will only sealingly close ifthe latches 214 are completely secured in the surrounding receptacles(not shown) in the housing structure around the aircraft door.

This is accomplished using an over-center system which operates based onthe angular position of shaft 519, and also uses a magnet 540 as anadditional retaining component. See FIG. 7C. In terms of specifics,adjacent collars 826 on the shaft 519 include downwardly-dependingspring-driven split levers 516 which are connected to wire portions 830of laterally displaced tandem torsion springs 832. Each spring 530 has acoil portion 832 and a lower wire 533. The lower wires 533 are securedinto the same outwardly extending flange 531 of the frame that is usedto support both ends of the short axle 536 that the door 522 pivots on.Each spring is under compression such that it has ends that push outwardagainst the outermost end of each split lever end 516, and against thepivot mount 524 on frame 531 at the other end.

Shaft 536 includes an outwardly extending tang 538 used to support amagnet 540 underneath. Magnet 540 can be either engaged with orangularly displaced from a metallic receiving pad 542 on the frame.

When spring-driven levers 516 are in an under-center position shown inFIGS. 7C and 8, the magnet will be angularly displaced form the metallicreceiving pad 542 on the frame. When in this state, the pressure ventdoor 522 is maintained in closed position.

But whether magnet 540 is displaced from or engaged with pad 542 willdepend on handle activation. More specifically, by pulling down eitherof inboard handle lever 311 or outboard handle lever 211 will causemagnet 540 to engage pad 542 and keep pressure vent door 522 fromreclosing absent ample contrary forces. The magnet function retains thevent door assembly in the open position if there are any mechanicalfailures that prevent the system from closing it due to any failuresthen existing mechanical system.

The torsion spring 530 works in concert with the magnet arrangement inproviding two maintainable states.

Initial Closed State.

In a first closed state, shown in FIGS. 1-8, the handles 211 and 311 arein closed position (as shown in FIGS. 1-5), and thus, vent door 522 isclosed. In this state, the torsion springs, in an under-center position,are pushing against levers 516 such that they cause shaft 519 to causeintegrated levers 828 to push member 520 against the door. The influencethe torsion springs have on the system can best be understood in lookingat both FIGS. 7C and 8.

Referring first to FIG. 8, whether the torsion springs tend to open orclose door 522 is dependent on the angular position of levers 516. Ifthe angular position of levers 516 is counterclockwise (see FIG. 8) ofan invisible center line (not shown) between the hinged attachmentlocation 524 on the bottom of each spring and the center axis 599 ofshaft 519, then the springs 530 will be “under-center.” If, however, theangular position of levers 516 is clockwise past this invisible centerline, the spring will be “over-center.” Whether springs 530 areunder-center (as shown in FIG. 8) or under-center (as in FIG. 6) willdetermine which way the springs compel the rotation of shaft 519.

In FIG. 8, levers 516 are shown as being under-center, in that they arenot clockwise past the center line between spring attachment 524 andcenter axis 599 of shaft 519. Because of that, the forces outwardagainst levers 516 will compel the door shut, and the magnet 540 will beremain displaced from receiving pad 542 unless some action is taken.

Transitioning to an Open State.

When either of the handles 211 or 311 is pulled down, the levers 516 onshaft 519 will move clockwise from the position shown in FIG. 8. Whenthe center axii of levers 516 (when looking in cross section) arerotated clockwise past the invisible line between the center of axis 599and spring connection points 524, this causes the springs 530 to beover-center. As a consequence, the forces provided by levers 516 willcause rotation of integrated levers 824 away from the vent door 522putting member 520 in tension. This tension pulls against the top ofpressure vent door 522, causing it to pivot out on its axle 536. At thesame time, tang 530 rotates such that magnet 540 is magneticallycompelled towards receiving pad 542. Even incremental movement of themagnet 540 towards the pad 542 increases the forces to the point thatthe initial tension created by the springs 530 being over-center isenough to snap open the door dynamically causing an almost instantpressure release. The magnet-to-pad retention forces, along with theover-center state of the springs, will keep the system in the open stateuntil the levers (211 and 311) are returned to closed state by a user.

The extent to which levers 211 or 311 must be pulled before the ventingprocess begins is not that great. Thus, the venting would be begin wellbefore the levers are fully opened, e.g., as is lever 211 in FIG. 9, butrather, shortly after being articulated outside of the latchingmechanism. That door 522 opens so suddenly is because the springs 530and levers 516 are oriented such that they create the over-center state(relative the center line) before the door latches 214 (see FIG. 4) areremoved from the receptacles (not shown) in the surrounding door housingso that the cabin pressure is released before the door will open.

Referring to FIG. 10, upon the opening of the pressure vent door, a bodyof air 1006 is allowed to escape from the inside of the aircraft cabinto the outside environment. Of the airflow paths shown in FIG. 10,outboard airflow 1008 occurs around the inboard handle assembly througha door cover assembly vent dam system 1100 (see FIGS. 11 and 12). System1100 increases the airflow in and around the handle lever 311 andrelease pawl 309 into the inboard handle assembly. The system comprisesa number of standoffs 1102 which are integral with a housing face 1104.The standoffs 1102 create a plurality of venting slots 1106 which willallow the additional airflow referred to above.

Once the air has traveled into the lever housing, the flow 1010 escapesthough an aperture 1002 existing in a back wall 1004 of the handlehousing. From there, the air continues along a path 1012 and then asmall fraction of the air escapes as subpaths 1114 going out of acentral aperture 908 and two lateral slots 906. Although not shown inFIG. 10, a central aperture 902 (see FIG. 9) exhausts most of the airfrom path 1012. The total air released is symbolically represented byexhausted flow arrow 1116.

FIG. 6 which shows the pressure vent door 522 in completely openposition, reveals the structural details existing during ventilationfrom inside the aircraft cabin. Referring to FIG. 6, a mesh screen 602is provided inside of where the pressure vent member 522 meets agasketed orifice 598. Screen 602 prevents the passage of largercontaminants which might cause mechanical or other problems if allowedto penetrate into the door system internals from the environment outsidethe aircraft. When the system is in open mode as shown in FIG. 6, thismesh screen 602 can be seen.

FIG. 9 shows an outside view of the outboard handle assembly 106 wherelever 211 has been pulled down. As can be seen in the figure, the airreleasing main central aperture 902, not visible in FIG. 10, is shownhere. It is provided in face of the back housing 904. Above that, thelateral elongated apertures 906 on each side of middle aperture 908 areall defined into a surface immediately underneath and inward front face904 of release pawl 209. These holes (holes 902, 906, 908) enable theflow of pressurized air out of the cabin upon activation of inboardlever 311 or outboard lever 211.

Reclosing of the Vent

When either of the handles (either 211 or 311) are returned from apulled position (e.g., as shown in FIGS. 6 and 9) towards a latchedposition (e.g., as seen in FIGS. 1-5 and 7A-D), the above-describedopening operations are reversed, which returns the system back to closedmode. More specifically, the reversed rotation of drive shaft 402 causeslinkage 403 to rotate outward (see FIG. 7B) causing component 405 tomove downward. This causes backbone (spine) 404 to drop back down. Thedrop of spine 404 causes the lever arrangements 406 (see FIG. 4) tomechanically cause the outward extension of securing latches 214 intothe reciprocating holes in the surrounding door housing. Once thesecuring latches 214 are fully extended into the receiving areas in thesurrounding door housing (not shown) aircraft door 102 is securely andsealingly held in the surrounding door jam.

Also resulting from the return of levers 211 and 311 towards latchedposition is that pressure relief door 522 is shut, sealing off the cabinso that it may be pressurized. When either lever is returned, the nowdownward moving extended pin 816 backbone 404 releases the catchportions 820/821 and then engages a reverse catch 877. This causes shaft519 to rotate back to its original (closed) position. This causes thepressure vent door 522 to return to shut position because the extendingintegrated levers 824 on collars 826 rotate back in putting member 520in compression. The force from member 520 compels the vent door 522towards its closed position.

But the reverse operations of the over-center system also have an effectin that they cause the vent door 522 to dramatically snap shut againstthe receiving gasket 602 (see FIG. 6) only after the door latches 214have been adequately engaged in the receptacles in the surrounding doorhousing. The return of shaft 519 to its original “closed mode” positioninitially overcomes the rotational forces of resistance when themovement of hinged door 522 causes tang 530 to raise lifting magnet 540off receiving pad 542.

This rotation also causes downwardly-depending spring-driven splitlevers 516 to move from their current over-center position back towardsan under-center position like that shown in FIGS. 7C and 8. Morespecifically, the angular position of levers 516, upon handle closure,moves counterclockwise (see FIG. 8) until reaching the invisible centerline (not shown) between the hinged attachment location 524 on thebottom of each spring and the center axis 599 of shaft 519. When thesprings 530 reach under-center, the torsion forces against levers 516have an immediate reverse effect on resistance, and the dramaticdifference results in an immediate snapping shut of the pressure ventdoor 522 against the seal 602 (see FIG. 6).

And the timing of this closure occurs because the springs 530 and levers516 are oriented such that they create an under-center state (relativethe center line) only after the door latches 214 (see FIG. 4) areadequately secured in the receptacles (not shown) in the surroundingdoor housing. Because of this, any human or mechanical failure inclosing the aircraft door 102 will cause the pressure vent door 522 toremain open. And when vent door 522 remains open, the pilot, whenreaching an appropriate altitude will detect a lack of cabin pressureand take appropriate safety measures.

It should be noted that although the embodiments depicted in thisapplication show a dual spring-driven lever 516 and spring pair 832arrangement, it is also, in other embodiments, possible to use a singlelever and spring. The disclosed embodiments use two to providestability. But the use of a pair of springs (e.g., pair 832) is notcritical. Thus, it is supported that the arrangement would still workwith at least one spring-driven lever and a single torsion spring.

In the disclosed embodiments herein, springs 530 are torsional springsinstalled such that they are compressed, and thus, have ends thatcompell outward. It should be noted, however, that that other kinds ofcompressible springs, e.g., helical compression springs or otheraxially-loaded springs or related devices could be used instead. Thus,the invention should not be limited to any particular device unlessspecified in the claims.

The pressure vent door 522 will also stay in open position (and thuswarn the pilot of problems) in the event of mechanical failures. If,e.g., any of (i) the mechanical equipment used to link the handles 211and 311 to drive shaft 402; (ii) the backbone 404 or mounted member 816;(iii) reverse catch 877; (iv) levers 516; or other components fail, thepressure vent door 522 will not close because the magnet arrangementwill hold it open.

Pawl Lock Assembly (Not Part of Door Vent System)

Another system of components are not relevant to the Door Vent Systemoperations, but are mentioned only so that these parts can be removedfrom consideration considering the complexity of the systems describedhere. They are, however, a part of a pawl-lock system that is in thegeneral environment with, but not mechanically involved with thedisclosed door vent system. Shaft 570 is used as part of the pawl-locksystem. This system works with a locking device 576 which is normallycaused to bear against the backbone 404 so that it can engage a catch572 in situations where one of backbone driving mechanisms 403, 812, and405 fail, or if shaft 402 fails. Or other failures that might cause thelatching/locking mechanisms to open due to upward movement of backbonewhich could otherwise cause the door to open in flight. This collateralpawl-lock system is designed to prevent against that.

Many different arrangements of the various components depicted, as wellas components not shown, are possible without departing from the spiritand scope of the present invention. Embodiments of the present inventionhave been described with the intent to be illustrative rather thanrestrictive. Alternative embodiments will become apparent to thoseskilled in the art that do not depart from its scope. A skilled artisanmay develop alternative means of implementing the aforementionedimprovements without departing from the scope of the present invention.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations and are contemplated within the scope of the claims. Notall steps listed in the various figures need be carried out in thespecific order described.

1. An aircraft door allowing access into an aircraft cabin, the aircraftdoor comprising: an inboard handle assembly; an outboard handleassembly; a flow path allowing air to pass into the inboard handleassembly and then out of the outboard handle assembly; a pressure ventdoor located in the flow path; the pressure vent door being opened uponthe operation of at least one of the inboard and outboard handleassemblies, the door when opened releasing pressure from the cabin. 2.The door of claim 1 wherein the inboard handle assembly includes aplurality of slots created by standoffs included between an interiorsurface of the aircraft and the handle assembly, the slots included inthe flow path.
 3. The door of claim 1 wherein the outboard handleassembly includes an air-exhausting aperture, and a plurality of smallerapertures located underneath a door latch to contribute to the flowpath.
 4. A pressure relief system for an aircraft door, the systemcomprising; a door handle mechanically connected to cause rotation of afirst shaft when activated; the rotation of the first shaft adapted toopen a pressure vent; a spring adapted to close the pressure vent whenin one of an under-center or over-center position; and the springadapted to open the pressure vent when in an other of the under-centerand over-center positions exists.
 5. The system of claim 4 wherein thepressure vent is on a pivot, and a magnet holds the pressure vent inopen position after the handle is pulled, and releases the pressure ventonly when the handle is returned and the door is closed.
 6. The systemof claim 4 comprising: a backbone member adapted to be translated uponrotation of the first shaft; a second shaft being rotated when thebackbone member is translated; a lever provided on the second shaft, thelever determining whether the spring is in an over-center orunder-center position depending on an angular position of the lever. 7.A door vent system for an aircraft comprising: an inboard lever foropening the door from inside the aircraft; an outboard lever for openingthe door from outside the aircraft; the inboard and outboard leversbeing mechanically coupled with a first shaft; a spine which is causedto translate in a first direction when the first shaft rotatates due tothe pulling of one of the inboard and outboard levers; a second shaftmechanically adapted to respond to receive a member on the spine whenthe spine is translated in the first direction and induce a firstdirection of rotation in the second shaft; a vent-pulling lever on thesecond shaft, the vent-pulling lever being linked to a pivotally-mountedvent door so as to pull the vent door open when the second shaft rotatesin the first direction of rotation, and to close the door when thesecond shaft rotates in a second direction; and an over-centerarrangement including a spring-driven lever on the second shaft, an endof the spring-driven lever receiving a force from a spring undercompression, the spring and a magnetic subsystem both compelling thevent door to open when the spring is over-center relative to thespring-driven lever, and the spring compelling the vent door shut whenthe spring is under-center if the second shaft moves in the seconddirection.
 8. A method of avoiding an unsafe pressure differentialbetween the outside and inside of an aircraft door, the methodcomprising: locating an inboard handle in an inboard handle housing onthe inside of the aircraft door; locating an outboard handle in anoutboard handle housing on the inside of the aircraft door; creating averitable airpath through both the inboard and outboard handle housings;and causing the airpath to open upon activation of either of the inboardor outboard handles.
 9. The method of claim 8 comprising: configuring aventillation system such that the airpath remains open unless the dooris secured.
 10. The method of claim 8 wherein the causing step furthercomprises: abrubtly opening a door vent to release air.
 11. The methodof claim 10 comprising: triggering the opening of the door vent by usinga mechanical system to cause a spring to become over-center to create areverse in leverage.
 12. The method of claim 8 comprising: using theactivation of either of the inboard or outboard handles to translate avertical member; and using the translation of the vertical member rotatea shaft to trigger the opening of a vent.
 13. A system for preventing anunsafe pressure differential between the outside and inside of anaircraft door, the system comprising: an inboard handle in an inboardhandle housing on the inside of the aircraft door; an outboard handle inan outboard handle housing on the inside of the aircraft door; anairpath through both the inboard and outboard handle housings; a ventcreated in the airpath; and an activation system which receivesmechanical movement of at least one of the inboard or outboard handlesand opens the vent to release air through the airpath.
 14. The system ofclaim 13 wherein the activation system comprises: a common shaft towhich both the inboard and outboard handles are coupled to and createrotion in when activated; a lower lever creating translation in a spinemember when the common shaft is rotated; an upper lever receiving thetranslation received from the spine member and rotating an upper shaft;and a reciprocating lever for flipping open a vent door upon therotation of the upper shaft.
 15. The system of claim 14 wherein theupper shaft rotating to an extent causes the upper lever to cause astate change in a spring to abrubtly open the door vent to release air.16. The system of claim 15 wherein the state change of the spring is oneof being over-center or under-center relative to the upper lever. 17.The system of claim 14 wherein a magnetic retention mechanism holds thedoor vent in open position until acted on by at least one of the inboardor outboard handles.
 18. The system of claim 13 wherein the ventincludes a vent door that is surrounded by a mesh material when openedto prevent the introduction of particles through the vent.
 19. Thesystem of claim 13 comprising: a safety-stop system adapted to preventsealing of the vent unless the door is properly latched.
 20. The systemof claim 18 wherein the safety stop system will not allow the vent doorto completely seal unless a plurality of securing latches disposedaround the aircraft door are completely extended into a plurality ofreceiving areas existing in surrounding door housing structures.
 21. Thesystem of claim 13 wherein the activation system includes an over-centerspring and lever subsystem acting in cooperation with a magnet-to-padretention mechanism to keep the vent door open until at least one of theinboard or outboard handles are returned to a closed state by a user.